wouldn't 3 x DPM's be better covering the range 19mm to 50mm (x 1.5 because of the crop)
That's really a question of does one prefer to carry three cameras over one camera that can use different lenses. The SD1 is also an APS-C sized sensor. While some would prefer the flexibility of a fast zoom on the SD1 to carrying three different cameras, I would guess that the "serious compact" crowd here might rather have 3 different cameras.
And the ability to use old M42 lenses like on the SD15 is restricted because the bigger sensor shows colorcasts on uncorrected lenses.
That's really a question of does one prefer to carry three cameras over one camera that can use different lenses. The SD1 is also an APS-C sized sensor. While some would prefer the flexibility of a fast zoom on the SD1 to carrying three different cameras, I would guess that the "serious compact" crowd here might rather have 3 different cameras.